The present invention relates to an air conditioner. More particularly, it relates to an air conditioner control system and control method thereof employing a pulse-width modulated compressor.
An air conditioner provides conditioned air by controlling the properties air such as room temperature and humidity of houses and buildings by means of a refrigeration cycle. Since people living and working in these houses and buildings differ from each other in their desired indoor conditions, and since the outdoor environment varies, the required cooling capacity may change frequently. In a multi-air unit conditioner having a plurality of indoor cooling units connected to a single outdoor unit, the respective indoor units differ from each other in the required cooling capacity. In most cases, since the respective indoor units may operate independently of one another, the total cooling capacity obtained by summing up the cooling capacity required from all the indoor units, tends to vary widely and unpredictably. A variable revolution compressor has been disclosed as a compressor that can vary its capacity in response to a variable cooling demand. In such a variable revolution compressor, the capacity of the compressor is regulated for a variation in required cooling capacity in such a way that the revolution of a motor is controlled by varying the frequency of current applied to the motor. However, the conventional variable revolution compressor is problematic in that the revolution of its motor cannot be controlled with a desirable responsiveness and accuracy because the operating motor has to be controlled directly according to a required cooling capacity. Additionally, since the revolution of the motor is frequently varied, vibrations and noises occur, shortening the life span of the motor and the compressor, and thus compromising the mechanical reliability of the entire system.
In addition, since an expensive and complicated circuit device and excessive power consumption are required in order to vary the frequency of the current applied to the motor, the conventional variable revolution compressor is less cost/energy efficient than a general compressor. Particularly, a conventional variable revolution compressor requires several power conversions, e.g., initially inputted commercial AC power into DC power, and the DC power into AC power having a required frequency, through converters, resulting in the structure of the circuit device being complicated and noises being generated frequently in the converter circuit devices.
In addition, a large-capacity variable revolution compressor is, particularly, problematic in that it is difficult to control the compressor, due to its low efficiency, large size and the high cost, so it is difficult to fulfill large-capacity requirements with a variable revolution compressor. Accordingly, in order to fulfill a large capacity requirement two or more compressors are employed. In this case, a standard compressor in which its motor is rotated at a constant speed is generally utilized together with the variable rotation number compressor. If a plurality of compressors is utilized, the entire size of an outdoor unit is enlarged and, accordingly, the handling of the outdoor unit becomes difficult.
Pulse width modulated(PWM) compressors are disclosed in, e.g., U.S. Pat. No. 6,047,557 and Japanese Unexamined Pat. Publication No. Hei 8-334094. These PWM compressors are utilized in refrigeration systems each having a plurality of freezing compartments or refrigerating compartments, and designed to be applied in short piping systems where the portion of a refrigerant conduit situated between a compressor and an evaporator is short. Consequently, these compressors cannot be directly applied to air conditioning systems for buildings that require long piping and are given control environments much different from those for the refrigeration systems. Heretofore, there has been a disclosure of a control system and method for utilizing a pulse width modulated compressor in an multi-air conditioner.
Accordingly, the present invention is directed to an air conditioner control system and control method thereof that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
It is an object of the present invention to provide an air conditioner control system, and control method thereof, employing a pulse-width modulated compressor, a single outdoor unit and plural indoor units relatively far from each other.
It is another object of the present invention to provide an air conditioner control system, and control method thereof, capable of calculating a required cooling capacity by computing a required cooling capacity for each respective indoor unit, and transmitting the computed cooling capacities to an outdoor unit, calculates the total required cooling capacity, and varying the capacity of the pulse-width modulated compressor in response to the calculated total cooling capacity requirement.
It is still another object of the present invention to provide an air conditioner control system having a pulse-width modulated compressor and plural evaporators, effectively designed to be suitable for air conditioning buildings.
In order to achieve the above objects, and in accordance with an aspect of the principles of the present invention, an air conditioner control system includes a compressor installed in an outdoor unit, said compressor being controlled by pulse-width modulation; a condenser connected to the compressor; a plurality of indoor units each having an evaporator, each evaporator being connected to the compressor and the condenser; indoor control units configured to calculate a respective required individual cooling capacity; and an outdoor control unit producing a duty cycle control signal in response to the required individual cooling capacities transmitted from respective one of said plurality of indoor control units, and controlling the capacity of the compressor in response to the duty cycle control signal.
According to another aspect of the present invention, an air conditioner control system includes a compressor having two states, each state corresponding to an operating capacity different from that of the other state, and configured to operate selectively in one of the two states while power is being applied thereto; a condenser connected to the compressor; one or more evaporators connected to the compressor and the condenser; a temperature sensor sensing an indoor temperature of a room being air conditioned; and a control unit configured to calculate required cooling capacity on the basis of the difference between said indoor temperature sensed by each temperature sensor and a preset temperature, said preset temperature being a desired indoor temperature for the room, and produce a duty cycle control signal based on the calculated required cooling capacity to control of the compressor to operate in one of said two states.
According to still another aspect of the present invention, an air conditioner control system includes a compressor having variable capacity and being controlled by pulse-width modulation; and a control unit configured to control variable capacity of the compressor wherein the control unit produces a duty cycle control signal which is a function of required cooling capacities transmitted from one or more indoor unit, to control the variable capacity of the compressor.
According to still another aspect of the present invention, a method of controlling an air conditioner having an outdoor unit with a pulse-width modulated compressor, and a plurality of indoor units each having an evaporator, includes: calculating required cooling capacities of the respective ones of said plurality of indoor units, under the control of the respective ones of said plurality of indoor units, transmitting the calculated required cooling capacities to the outdoor unit, adding the required cooling capacities transmitted from the respective indoor units together under the control of the outdoor unit to produce a total required cooling capacity, and producing a duty cycle control signal which is a function of the total required cooling capacity; and controlling the capacity of the compressor in response to the duty cycle control signal.
According to still another aspect of the present invention, a method of controlling an air conditioner having an outdoor unit with a pulse-width modulated compressor, and an evaporator installed in a room being air conditioned, comprising: sensing indoor temperatures of the room, finding a difference between the sensed indoor temperature and a preset temperature, said preset temperature being is a desired indoor temperature, calculating required cooling capacities on the basis of the difference, producing a duty cycle control signal as is a function of the calculated required cooling capacity, and controlling the capacity of the compressor in response to the duty cycle control signal.